1. Field of the Invention
This invention pertains to a wobble press having a first die half which is driven by a drive, relative to the longitudinal axis of the press, wobbly around a fulcrum point, and which includes a movable second half die axially parallel relative to the first die half wherein the wobble drive includes hydraulic working pistons which are provided with a regular, defined, pulsating flow of a hydraulic medium and which on their part are connected with the first die half for the generation of a wobble movement.
2. Discussion of the Background of the Invention and Material Information
Such a wobble press is, for example, shown in Swiss Patent Publications CH 662983 and CH 666857 or German Patent Publication DE 1652653 as well as U.S. Pat. No. 4,984,443 to Sato et al and serves for the production of massive parts of metal or other rigid materials, wherein the part or the workpiece is formed between two enveloping tools or die parts wherein, in opposition to the parallel axial press methods the one die half carries out a rolling type of wobbly movement. Due to the partial contact of the upper die with the workpiece material the workpiece material can, via the wobble movement be brought to movement with substantially less press force so that in one step substantially greater degrees of deformation and a more exacting forming of the matrix contours may be achieved. The possible feed advance during contact is determined by the angle of inclination of the wobbling tool and is thus correspondingly limited. The magnitude of this advance determines the total working stroke, i.e., for the desired degree of forming the required number of wobble passes and the corresponding wobble frequency determines the time of forming.
In known wobble presses, the utilization of mechanical drives for the wobble movement limits the rotational frequency or wobble frequency through a number of factors:
In the transverse setting of the wobbling tool disturbing centrifugal forces originate which particularly emanate also from the large mass of the eccentric shaft and the eccentric drive components. These free forces produce prohibitive vibrations, at higher wobble frequencies, between the tool parts, thus restricting the wobble frequency in known wobble presses to low values.
The cup shaped bearing of the wobbling tool must in addition thereto absorb the entire press thrust. Due to the cup shaped formation of the upper pressure bearing the bearing pressure increases per unit area and thus considerably increases the work produced due to friction. The thus produced frictional heat must be removed through a thin oil film from the bearing clearance. With increasing wobble frequencies the friction heating increases in an analog manner, which heat must be removed through the lubricating means. On the other hand, the narrow bearing clearance limits the through-put flow of the lubrication and cooling means.
The insufficient heat removal and the centrifugal forces of the off center mass prohibit, in known constructions, the utilization of wobble frequencies more than approximately 600 revolutions per minute. If the permitted advance per wobble cycle is not exceeded, workpieces of medium dimension are turned out in forming times of approximately 4 to 5 seconds with a corresponding production capacity of only 10-12 parts per minute. Trials at this limited wobble frequency to reduce deformation time via the increase in the closing speed of the press, did however lead to an increase in the contact area between the workpiece and the wobble tool. In this instance a total press force would be required which is the same magnitude as in axially parallel presses so that the wobble press can in this instance not provide an essential advantage.